I have driven accoss the border many times without a problem, but when they ask about your boats on the fifth or sixth or tenth time and you can not prove you own it or you did not purchase it in the other country, you will wish you had the proof.

As for the micro dots, the Canadian Customs used to put a label sticker in your boat as you crossed so you could prove it was yours on return, just as they do for your cameras, electronics, etc., but to my understanding from Customs,they no longer do this. I could be wrong or misled or thinking of another label. Better safe than sorry.